EP 2 196 232 A1 describes a drive mechanism for a medication delivery device comprising a housing having a proximal end and a distal end, a rotation member which is rotated in a first direction during setting of a dose and rotated in an opposite second direction during delivery of the dose, a piston rod, which is adapted to be displaced in a distal direction with respect to the housing for delivering the dose, a drive member, which follows rotational movement of the rotation member in the second direction during delivery of the dose, and a stop member, which prevents rotational movement of the drive member with respect to the housing in the first direction during setting of the dose. The rotational movement of the drive member in the second direction is converted into movement of the piston rod in the distal direction with respect to the housing. The medication delivery device is provided with the drive mechanism and with a cartridge containing the medication. An empty cartridge can be replaced with a new cartridge, so that the medication delivery device is reusable. The replacement of the cartridge requires a reset of the piston rod to an initial position at the proximal end. A priming operation is performed to bring the piston rod in contact with the piston of the new cartridge.
U.S. Pat. No. 6,277,099 describes a medication delivery device comprising a lead screw for medication delivery. A priming operation required after a change of the cartridge is supported by the lead screw being forward biased by a lead screw spring.